Alexa collects information on Web usage through the Windows-only application, the Alexa Toolbar. This allows them to provide statistics on web site traffic, as well as related link information. The Alexa Toolbar has a bad reputation with anti-spyware programs, as it collects information on search habits.

In 1999, Alexa was acquired by Amazon.com for about $250 million in Amazon stock. The "site info" link on the Alexa site lists related links for websites and also records how much web traffic they receive. Alexa began a partnership with Google in spring2002, and with the Open Directory Project in January2003. Today, Alexa is primarily a Google-based search engine, an Open Directory-based web directory, and a supplier of site information.

In December 2005, Alexa opened its extensive search index and web-crawling facilities to third party programs through a comprehensive set of web services and APIs. These could be used for instance to construct vertical search engines that could run on Alexa's own servers or elsewhere.